Neural crest cells appear on the edges of the neural tube and spread throughout the embryo, giving rise to all of the following structures except . Neural crest cells appear on the edges of the neural tube and spread throughout the embryo, giving rise to all of the following structures except . pharyngeal slits (or clefts) of invertebrate chordates some of the bones and cartilage of the skull sensory capsules in which eyes and other sense organs develop. teeth

a "theory" a suggestion that is not 100 % accurate, or a figure. some people say its a theory because they of all the passed theory's about one subject. it depends sometimes theory might be accurate and sometimes they are.

photosynthesis makes the glucose that is used in cellular respiration to make atp. the glucose is then turned back into carbon dioxide, which is used in photosynthesis. while water is broken down to form oxygen during photosynthesis, in cellular respiration oxygen is combined with hydrogen to form water.